# FE_DIVBYZERO, FE_INEXACT, FE_INVALID, FE_OVERFLOW, FE_UNDERFLOW, FE_ALL_EXCEPT

From cppreference.com
< cpp‎ | numeric‎ | fenv

Defined in header `<cfenv>` |  |
#define FE_DIVBYZERO /*implementation defined power of 2*/ |  | (since C++11)
#define FE_INEXACT /*implementation defined power of 2*/ |  | (since C++11)
#define FE_INVALID /*implementation defined power of 2*/ |  | (since C++11)
#define FE_OVERFLOW /*implementation defined power of 2*/ |  | (since C++11)
#define FE_UNDERFLOW /*implementation defined power of 2*/ |  | (since C++11)
#define FE_ALL_EXCEPT FE_DIVBYZERO | FE_INEXACT | \ FE_INVALID | FE_OVERFLOW | \ FE_UNDERFLOW |  | (since C++11)

All these macro constants (except `FE_ALL_EXCEPT`) expand to integer constant expressions that are distinct powers of 2, which uniquely identify all supported floating-point exceptions. Each macro is defined only if it is supported.

The macro constant `FE_ALL_EXCEPT`, which expands to the bitwise OR of all other `FE_*`, is always defined and is zero if floating-point exceptions are not supported by the implementation.

Constant | Explanation
`FE_DIVBYZERO` | pole error occurred in an earlier floating-point operation
`FE_INEXACT` | inexact result: rounding was necessary to store the result of an earlier floating-point operation
`FE_INVALID` | domain error occurred in an earlier floating-point operation
`FE_OVERFLOW` | the result of the earlier floating-point operation was too large to be representable
`FE_UNDERFLOW` | the result of the earlier floating-point operation was subnormal with a loss of precision
`FE_ALL_EXCEPT` | bitwise OR of all supported floating-point exceptions

The implementation may define additional macro constants in `<cfenv>` to identify additional floating-point exceptions. All such constants begin with `FE_` followed by at least one uppercase letter.

See math_errhandling for further details.

### Example

Run this code

    #include <cfenv>
    #include <cmath>
    #include <iostream>

    // #pragma STDC FENV_ACCESS ON

    volatile double zero = 0.0; // volatile not needed where FENV_ACCESS is supported
    volatile double one = 1.0;  // volatile not needed where FENV_ACCESS is supported

    int main()
    {
        std::feclearexcept(FE_ALL_EXCEPT);
        std::cout <<  "1.0/0.0 = " << 1.0 / zero << '\n';
        if (std::fetestexcept(FE_DIVBYZERO))
            std::cout << "division by zero reported\n";
        else
            std::cout << "division by zero not reported\n";

        std::feclearexcept(FE_ALL_EXCEPT);
        std::cout << "1.0/10 = " << one / 10 << '\n';
        if (std::fetestexcept(FE_INEXACT))
            std::cout << "inexact result reported\n";
        else
            std::cout << "inexact result not reported\n";

        std::feclearexcept(FE_ALL_EXCEPT);
        std::cout << "sqrt(-1) = " << std::sqrt(-1) << '\n';
        if (std::fetestexcept(FE_INVALID))
            std::cout << "invalid result reported\n";
        else
            std::cout << "invalid result not reported\n";
    }

Possible output:

    1.0/0.0 = inf
    division by zero reported
    1.0/10 = 0.1
    inexact result reported
    sqrt(-1) = -nan
    invalid result reported

### See also

math_errhandlingMATH_ERRNOMATH_ERREXCEPT (C++11)(C++11)(C++11) | defines the error handling mechanism used by the common mathematical functions (macro constant)
C documentation for floating point exception macros

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/numeric/fenv/FE_exceptions&oldid=169745"